1. Field of the Invention
The present invention relates to an improved rocker lubrication arrangement which is intended particularly, but not exclusively, for use in an internal combustion (i.c.) engine.
2. Discussion of the Related Art
Lubrication of a rocker arm assembly can be by means of an oil mist generated within an engine housing. The oil mist coats engine components lubricating any surfaces of contact between them. The mist may not reach into the upper regions of the housing below the engine cover. This can result in the metal to metal contacts at both ends of the rocker arms remaining dry leading to excessive wear and the need for frequent readjustment and replacement of parts.
One solution to this problem has been to drill oil channels laterally through the bosses of the rocker arms. The channels each communicate at first ends with an oil supply passage in the rocker arm support shaft, which normally provides a supply of oil to lubricate rocker arm bushes, and each exit at second ends at appropriate points on the rocker arm bodies to supply oil to the push rod ball joints and rocker arm ends contacting valve stem assemblies. This solution is expensive since the rocker arms are often formed of cast or forged metal and drilling of this material is difficult, particularly bearing in mind the narrow diameters of the drilled channels compared to their relatively long lengths. There is considerable wastage of rocker arms during the machining process due to broken drill bits, for example.
A further problem is that the casting or forging tolerances must be closely controlled to ensure that the drilled holes run centrally down the bosses.